France's Louvre museum has shut down one of its galleries after a woman vandalised an iconic painting by Delacroix by writing on it with a black marker.

The 28-year-old woman was apprehended by an attendant late on Thursday after scrawling "AE911" on Liberty Leading the People, which was on show in the Louvre's recently-opened museum in the northern town of Lens.

It was not immediately clear what the slogan meant.

On Friday the Louvre said it was temporarily closing the wing of the gallery where the painting was being displayed.

It said a specialist art restorer was being sent to the site but it believed the damage was not significant and could be easily repaired.

A prosecutor in the nearby town of Bethune said he had asked for a psychiatric evaluation of the young woman, who appeared to be "unbalanced".

He said her reasons for defacing the painting were not yet clear.

The painting by Delacroix commemorates France's July Revolution of 1830.

It shows a bare-breasted woman personifying Liberty leading the people forward over the bodies of the fallen.

She is holding the French tricolour in one hand and a bayonetted musket in the other.